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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <input type="button" value="点击"> 

   
    <script>
    //3. 有一个按钮，它上面没有处理程序。执行以下代码之后，哪些处理程序会在按钮被点击时运行？会显示哪些 alert ？
    let butt=document.querySelector('botton');
    butt.addEventListener("click", () => alert("1"));
    butt.removeEventListener("click", () => alert("1"));
    butt.onclick = () => alert(2);
    </script>
</body>
</html>